bcma: use custom printing functions

Having bus number printed makes it much easier to anaylze logs on
systems with more buses. For example Netgear WNDR4500 has 3 AMBA buses
in total, which makes standard log really messy.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>